Is it possible that I'm pregnant?

I had unprotected the day I was suppose to get my period (which would be this past Thursday). This was the very first time I had , so I experienced some bleeding due to my hymen being broken. The next day I got my period, but it wasn't as heavy as it normally is. Normally my period lasts about six days, but now it's light, as if it's the end of my cycle. Now I'm absolutely petrified that I'm pregnant & I really need opinions. Please & thanks!